In recent years, a communication system using a technology of near field wireless communication is rapidly becoming popular. In this kind of communication system, a portable device equipped with near field wireless communication function (e.g. mobile phones and Contact-Less ICs (Integrated Circuit) card) and an external device (e.g. IC card readers/writers) can communicate each other by the near field wireless communication.
Communications among these devices using the near field wireless communication do not require a physical contact between the devices. Therefore, even if obstacles may exist between these devices, in the case that the obstacles do not shelter electromagnetic wave, it is possible to communicate between the devices.
Accordingly, for example, in the case of installing and using a passenger ticket function of a train or bus on a portable device, a passenger can get an advantage that he/she merely places the portable device over an IC card reader/writer which is installed in an automatic ticket gate, when he/she passes the ticket gate.
Moreover, the IC card reader/writer of this kind of automatic ticket gate has less attrition compared with the automatic ticket gate having a driving mechanism for inserting and extracting the passenger ticket or a season pass. Accordingly, it can get advantages including such as reducing a maintenance cost and keeping high availability.
However, while a feature of the communication control apparatus using the near field wireless communication can have the above-mentioned merits, it leaves a problem that a malicious third party may try to access information in the portable device of a holder of the portable device without being noticed. For example, in the case that a person puts the Contact-Less IC card in a pocket and gets on a train, it is sufficiently possible that a malicious third party hides an IC card reader/writer, approaches the person and tries an illegal access to the Contact-Less IC card in the pocket.
As a measure to this kind of illegal access, a method can be considered wherein it detects an action that the above-mentioned holder of the portable device places the portable device over the external device, and thereby it judges a presence of intention to use of the holder's portable device.
A technology of realizing the above-mentioned method is disclosed in the patent document 1. The IC card with an illegal access prevention function disclosed in the patent document 1 has sensor means, movement information measuring means and movement model comparing means. The sensor means measures a motion. The movement information measuring means acquires movement information of the IC card with illegal access prevention function by a measured value of the sensor means. The movement model comparing means compares the movement information with a predefined movement model.
Then, the IC card with an illegal access prevention function disclosed in the patent document 1 judges whether or not the holder of the IC card with illegal access prevention function has an intention to use the IC card based on the comparison result. Further, the IC card with illegal access prevention function sets its state of whether or not it enables the communication based on the judgment.
The patent document 2 disclosed a RFID (Radio Frequency IDentification) tag distance measuring system which measures a distance from the card reader to the RFID tag using a communication function with the RFID tag.
The patent document 3 disclosed a tag communication apparatus which executes wireless communication with a RFID tag, and a position measuring unit which calculates a distance from the tag communication apparatus to the RFID tag.
The patent document 4 disclosed a method where a reader emits a near field status signal using such as a magnetic signal, an optical signal and an acoustic signal, and a transponder enables data transmission when the near field signal is detected.